Liquid ink printers of the type frequently referred to as continuous stream or as drop-on-demand, such as piezoelectric, acoustic, phase change wax-based or thermal, have at least one printhead having drop ejectors from which droplets of ink are directed towards a recording sheet. Within the printhead, the ink is contained in a plurality of channels. Power pulses cause the droplets of ink to be expelled as required from orifices or nozzles at the end of the channels.
In a thermal ink-jet printer, the power pulses are usually produced by resistors, each located in a respective one of the channels, which are individually addressable to heat and vaporize ink in the channels. As voltage is applied across a selected resistor, a vapor bubble grows in the associated channel and initially the ink bulges from the channel orifice. The bubble quickly collapses and the ink within the channel then retracts and separates from the bulging ink thereby forming a droplet moving in a direction away from the channel orifice and towards the recording medium whereupon hitting the recording medium a dot or spot of ink is deposited. The channel is then refilled by capillary action, which, in turn, draws ink from a supply container of liquid ink. Operation of a thermal ink-jet printer is described in, for example, U.S. Pat. No. 4,849,774.
The ink jet printhead may be incorporated into either a carriage type printer, a partial width array type printer, or a page-width type printer. The carriage type printer typically has one or more relatively small printheads containing the ink channels and nozzles. The printheads can be sealingly attached to one or more disposable ink supply cartridges and the combined printheads and cartridge assembly is attached to a carriage which is reciprocated to print one swath of information (equal to the length of a column of nozzles), at a time, on a stationary recording medium, such as paper or a transparency. After the swath is printed, the paper can be stepped a distance equal to the height of the printed swath or a portion thereof, so that the next printed swath is contiguous or overlapping therewith. This procedure is repeated until the entire page is printed.
In contrast, the page width printer includes a stationary printhead having a length sufficient to print across the width or length of a sheet of recording medium at a time. The recording medium is continually moved past the page width printhead in a direction substantially normal to the printhead length and at a constant or varying speed during the printing process. A page width ink-jet printer is described, for instance, in U.S. Pat. No. 5,192,959.
Printers typically print information received from an image output device such as a personal computer. Typically, these output devices generate pages of information in which each page is in the form of a page description language (PDL). An electronic subsystem (ESS) in the printer transforms the page description language into a raster scan image which is then transmitted to a peripheral or image output terminal (IOT). The raster scan image includes a series of scan lines in which each scan line contains information sufficient to print a single line of information across a page in a linear fashion. In the page description language, printed pages also include information arranged in scan lines.
In known thermal ink jet printheads or printbars which print a single line of pixels in a burst of several banks of nozzles, each bank prints a segment of a line. The banks of nozzles are typically fired sequentially and the nozzles within a bank are fired simultaneously. An ink jet printbar having banks of nozzles is described in U.S. Pat. No. 5,300,968 to Hawkins, incorporated herein by reference. These printbars include a plurality of printhead dies, wherein each die prints a portion of a line. Within the die, the banks of nozzles print a segment of the portion of the line. Many printing devices, including xerographic printers having a laser raster output scanner, use information in raster scan format to print the image without performing manipulation of the image data received. The architecture of liquid ink printheads, however, being dependent on the sequential firing of banks of nozzles and the simultaneously fired nozzles within a bank requires some type of manipulation of the image information. Historically, the necessary data manipulation has been done with software. Software processing performed the manipulation before the data was shipped to the printhead. These processes, however, can be time consuming and not very efficient.
Various printers and methods for manipulating image data for printing on a recording medium are illustrated and described in the following disclosures which may be relevant to certain aspects of the present invention.
U.S. Pat. No. 4,567,570 to Peer describes a logic network and method for processing columns of vertically oriented image data bits to produce control signals for operating a linearly slanted printhead. The network and method includes writing different equal byte segments of each column into a RAM memory while preskewing successive bytes, respectively, from one another by the equivalent of the number of columns of print resolution capability between successive print elements of the printhead represented by each byte.
U.S. Pat. No. 5,016,190 to Thomson describes a method and apparatus for converting data representative of a plurality of cells arranged independently of one another on a page into data in raster scan order for subsequent printing. Cell data for individual cells is fetched in an order dependent on the line of raster scan where the cell first appears in the bit position for the first bit representing the cell.
U.S. Pat. No. 5,579,453 to Lindenfelser describes a smart direct memory access controller for data transformation. The controller is used in computer systems to read and/or write data in a non-linear fashion in order to alter the organization of data stored within the computer system.
U.S. Pat. No. 5,619,622 to Audi et al. describes a full width array raster imaging interface for an ink jet printer. The raster imaging interface transforms raster information for printing by a thermal ink jet full width array printbar.